1. Field of the Invention
The invention generally relates to an optical module and an optical system, and more particularly, to a wavelength conversion wheel module and an illumination system.
2. Description of Related Art
In recent years, projection devices with solid state light sources, such as light-emitting diodes (LED) and laser diodes, have gradually gained their market share. LEDs have a luminous efficiency between 5% and 8% and come with different luminous spectra, such as a red spectrum, a green spectrum, and a blue spectrum. LEDs offer excellent luminous spectra (i.e., luminous spectra with high spectral peak values and small spectral widths), and are used as the pure color light sources in projectors.
On the other hand, laser diodes have a luminous efficiency over 20%. To break the limit of LED light source, a technique of exciting phosphor with a laser light source to generate the pure color light source desired by a projection device has been developed. The two techniques mentioned above are the mainstream of today's solid state light source for projection devices.
In order to achieve a high enough output brightness in a laser projection device, multiple laser arrays are adopted and focused on a phosphor layer to generate an intensive fluorescent light output. This array formed by arranging laser diodes offers a very high light output power for exciting phosphor, and has advantage of flexibility in adjusting the number of light sources such that the needs of different projection brightness would be satisfied. Thereby, projection devices with such light source are highly potential and will replace the conventional projection devices with ultra high pressure (UHP) lamps as their light sources of the mainstream projection devices.
An image projecting system including an illuminating device, an illumination optical system, a spatial modulation element, and a projection optical system is disclosed in U.S. Pat. No. 7,461,950. An illumination system adapted to a projector is disclosed in U.S. Publication No. 2012/0039065, where the illumination system includes a blue laser light source, a phosphor wheel, and a spectroscope disposed between the blue laser light source and the phosphor wheel. A micro-lens projection system including a light source, an integral rod, a multi-mode color wheel, a spatial light modulator, a total internal reflection prism, and a projection lens is disclosed in U.S. Pat. No. 6,813,087. A transmissive semiconductor light source device adapted to a projector is disclosed in U.S. Publication No. 2011/0116253, where the transmissive semiconductor light source device includes a semiconductor light source that emits an ultraviolet light beam along an optical axis, a phosphor wheel perpendicular to the optical axis, a motor for rotating the phosphor wheel around a shaft, and an actuation module. A color wheel device which can be conveniently dissembled and replaced is disclosed in U.S. Pat. No. 7,052,146.